1. Field of the Invention
The present invention relates to an intruding-object detection apparatus for detecting an object intruding into a field of view using a stereo camera.
2. Description of the Related Art
The applications of image recognition techniques include an intruding-object detection apparatus for detecting an object intruding into the field of view of a camera. For example, Japanese Unexamined Patent Application Publication No. 5-16811 discloses a system for detecting an obstacle which intrudes into a railroad crossing on the basis of images taken by cameras. According to this related art, background images taken by two cameras are aligned. After that, whether an object exists in the railroad crossing is determined by a correlation process based on one-dimensional Fourie transformation. In addition, Japanese Unexamined Patent Application Publication No. 8-317373 discloses a technique of detecting an object intruding into a field of view using variations in illumination of monochrome images taken by a single camera. Japanese Unexamined Patent Application Publication No. 9-282569 discloses a technique similar to the above.
According to the former related art, images are corrected in alignment using ground serving as a single plane as a reference. Accordingly, when fixed objects which lie on the ground but are not subjects to be detected, for example, a wall, a fence, weeds, and various devices existing in the vicinity of the railroad crossing are included in the field of view, these objects may be detected as intruding objects by mistake.
According to the latter related art whereby an intruding object is detected using variations in illumination of monochrome images, it is fundamentally difficult to completely eliminate false detection or a detection error with respect to an object on the basis of a fluctuation of environmental illumination.